We all know that laser diode is widely used, so do you know what its main working principle is? Let's take a look at it together.

A laser diode is basically "putting light into a resonant cavity"

Laser is called "laser" because it is different from the light emitted by ordinary LED.

Squeeze a bunch of electrons and holes in the PN junction, let them recombine constantly, turn energy into light, and then this light bounces back in the cavity, bouncing more orderly and stronger, and finally rushes out from one end, which is the laser.

The structure of laser diode is very similar to that of ordinary diode, and the core is PN junction.

But the material and structure of laser diode are more exquisite, because it should ensure that:

Electrons and holes can be concentrated in a certain layer; When recombination, it releases light with fixed wavelength; Photons can be used by cavities instead of running around.

Optical resonator (Fabry-Perot cavity) is the core of "laser"

Not all light-emitting diodes are called lasers, but the key lies in this cavity.

The chip end faces on both sides of the laser diode are as smooth as mirrors (surfaces naturally cleaved by wafers), and the left and right sides are natural mirrors.

Light is reflected back and forth inside, then superimposed with the generated light, layer by layer, and finally enhanced to a certain extent, and then emitted from one end.

The current must exceed the "threshold current" before the laser actually appears.

Before reaching the threshold current, LD is actually a brighter LED.

At the moment of threshold current, the "positive feedback" of stimulated radiation is formed in the cavity, and the light quantity jumps immediately and begins to enter the real laser mode.

The above is the working principle of laser diode. If you still don't understand, please feel free to contact us.